Such immersion sensors are known from JP-A1 61-60154. The immersion sensors, described therein, have a metal wire as a support pin, which at its one end is embedded into a mounting material. On its other end the support pin is also coated with a reference material of a metal-metal oxide. On top of this reference material is a layer of a solid electrolyte material. The support pin at its mounted end is coated with a refractory material, which on the one side reaches into the mounting material and on the other side extends to the solid electrolyte material, whereby the solid electrolyte material can be partially covered by the refractory material.
In such a construction the refractory material can corrode in the molten metal, whereby in the area outside of the mounting material where the refractory material touches the solid electrolyte material, the immersion sensor can change its electrochemical properties. As a result drastic changes occur in this area during the initial measuring phase of the EMF (electromotive force) measuring procedure, so that a constant EMF reading is only observed after a long immersion period or not at all. If there is an overlapping of the solid electrolyte material by the refractory material, then an additional EMF, which arises in an area extending below the refractory material, is being measured. This area is undefined and therefore leads to a distortion of the values when measuring the EMF.
A similar immersion sensor with the above described layer construction is also known from JP-A1 60-3053. With this construction also the above described inaccuracies occur.
In view of the above prior art it is the purpose of the present invention to produce an immersion sensor, which reaches a stable EMF-value after a short immersion period. An additional object of the invention is to develop a process for the manufacture of an intermediate for such an immersion sensor.